Abstract/Project Summary Active remodeling of adherens junctions is crucial not only for keeping tissue integrity but also for driving the progression of many developmental events such as epithelial-mesenchymal-transition (EMT). Recent development in the research at the interface between cell biology and mechanical force has revealed that, in addition to the well studied biochemical signals, the mechanical tension plays an critical yet unappreciated role in the regulation of adherens junctions. The candidate's postdoc study has demonstrated that during Drosophila gastrulation adherens junctions in mesodermal primordium are repositioned and strengthened in response to apically localized myosin contraction. Such tension- dependent remodeling of adherens junctions protects junctions from Snail-driven junction disassembly and appear to developmentally time the EMT to occur only after the completion of the morphogenetic event. This establishes a model to study the mechanosensitive regulation of adherens junctions in an intact developmental system. The goal of the project is to elucidate the mechanism of tension-dependent adherens junction remodeling in the context of EMT. In the first aim, the dynamics of junctional components within individual junction clusters during the remodeling will be examined using photoconvertible fluorescent probes and in vivo junctional tension will be measured in live embryos using a FLIM (Fluorescence Lifetime Imaging Microscopy)-based FRET tension sensor that have been recently made and tested. In the second aim, a small yet comprehensive pool of direct Snail target genes identified from a recent genome-wide study will be tested for their roles in Snail-dependent junction disassembly. The identified genes will be further characterized in the independent phase. The last aim is to test the principle of tension-dependent junction remodeling and its impact on EMT in vertebrate cell lines in collaboration with McClatchey's lab. The cell lines with stably expressed live imaging markers will be made during the mentored phase. Junction dynamics and the role of mechanosensitive junction remodeling during EMT will be examined in the independent phase. Result from this project will advance our understanding on regulation of adherens junctions in response to myosin-generated tension and shed light on the novel function of Snail on disassembling junctions at post-transcriptional level during EMT.